Most peo­ple like to eval­u­ate them­selves using var­i­ous tests, for­mu­las and index­es — it is always inter­est­ing to learn some­thing new about your­self. It is not sur­pris­ing that there are many indices in the world for cal­cu­lat­ing nor­mal weight. But does at least one of them give real data on what should be the ide­al weight of a giv­en per­son?

Med­AboutMe breaks down the four most pop­u­lar ide­al weight cal­cu­la­tion meth­ods and finds out what are their draw­backs and should they be trust­ed?

Body mass index

Body mass index

Body mass index (BMI, BMI) is the most pop­u­lar and best known for­mu­la for esti­mat­ing a per­son­’s body weight. The for­mu­la includes an indi­ca­tor of weight and height: weight in kilo­grams should be divid­ed by the square of height in meters (kg / m2). Accord­ing­ly, we get:

  • BMI less than 18.5 kg / m2 — a per­son is under­weight.
  • BMI from 18.5 to 24.9 kg / m2 — ide­al weight.
  • BMI from 25 to 29.9 kg / m2 — over­weight.
  • BMI over 30 kg/m2 — obe­si­ty.

The biggest plus of BMI is its sim­plic­i­ty. Any­one can mea­sure their height and weight with the help of the sim­plest tools that are always at hand.

The biggest dis­ad­van­tage of BMI is that it does not take into account the full vari­ety of vari­a­tions in the human body.

  • BMI does not reflect the changes that occur with age, when mus­cles atro­phy, the amount of fat increas­es, and a per­son­’s height becomes small­er due to degen­er­a­tive process­es in the spine. That is, BMI for old­er peo­ple will show an under­es­ti­mat­ed result.
  • BMI does not take into account the body struc­ture of ath­letes, in which the per­cent­age of lighter fat is low, and the pro­por­tion of heav­ier mus­cles is high. BMI for ath­letes will show an over­es­ti­mat­ed result.
  • Not all BMI cal­cu­la­tors offer to indi­cate the gen­der of a per­son. But it is known that a woman with equal height with a man will have more fat, but less mus­cle, and togeth­er the ratio of these tis­sues will sig­nif­i­cant­ly affect the final BMI.

In a 2001 study by a group of sci­en­tists from Italy and Hol­land, it was shown that the sen­si­tiv­i­ty and speci­fici­ty of BMI as a method of deter­min­ing the lev­el of body fat is quite low.

Thus, accord­ing to BMI cal­cu­la­tions, obe­si­ty was detect­ed in 25% of men par­tic­i­pat­ing in the study and in 35% of women. How­ev­er, a sur­vey using the den­sit­o­m­e­try method showed that 8% of men and 7% of women from the total sam­ple who fell into the obe­si­ty group accord­ing to BMI did not actu­al­ly have it, indi­cat­ing a low speci­fici­ty of the method.

When assess­ing the sen­si­tiv­i­ty of BMI, the results were even worse: false-neg­a­tive BMI results were found for 41% of men and 32% of women.

Waist/Hip Index

Waist-to-hip ratio (WHR), or waist/hip index (WHI) is a fair­ly well-known method for assess­ing the degree of abdom­i­nal obe­si­ty, that is, obe­si­ty in which fat is active­ly deposit­ed in the abdomen.

In order to cal­cu­late it, you should mea­sure the waist in its nar­row­est part (if there is none, 2 cm above the navel), and divide the result­ing val­ue by the vol­ume of the hips in their widest part.

The high­er the degree of abdom­i­nal obe­si­ty and the high­er the TTB score, the high­er the risk of devel­op­ing dia­betes and car­dio­vas­cu­lar dis­ease.

Since the fig­ures in men and women have pro­nounced gen­der char­ac­ter­is­tics, FTI should be con­sid­ered sep­a­rate­ly for men and sep­a­rate­ly for women.

For women, the fol­low­ing data can be used:

  • FTI less than 0.80 — nor­mal weight.
  • FTI from 0.80 to 0.84 — over­weight.
  • FTI more than 0.85 — obe­si­ty.

For men, the results will be as fol­lows:

  • FTI less than 0.90 — nor­mal weight.
  • FTI from 0.90 to 0.99 — over­weight.
  • FTI more than 1.00 — obe­si­ty.

The most sig­nif­i­cant plus of ITB is the assess­ment of car­diac risk, which is high­ly cor­re­lat­ed with gra­da­tion by weight. In accor­dance with the above data, with nor­mal weight, the risk of devel­op­ing heart and vas­cu­lar dis­eases is low, with excess weight — mod­er­ate, and with obe­si­ty — high. TPI is also used to assess the risk of type 2 dia­betes.

The most sig­nif­i­cant dis­ad­van­tage of ITB is that this indi­ca­tor does not take into account the fea­tures of the human fig­ure. It also does not allow you to esti­mate the per­cent­age of fat in the human body and com­pare it with the pro­por­tion of mus­cle mass.


In 2016, sci­en­tists from Malaysia pub­lished an arti­cle in the Inter­na­tion­al Jour­nal of Pre­ven­tive Med­i­cine prov­ing that the mea­sure­ment of waist cir­cum­fer­ence (WC, WC) is a more accu­rate indi­ca­tor of abdom­i­nal obe­si­ty com­pared to FTB. Sci­en­tists explain this by the fact that ITB can be under­es­ti­mat­ed in peo­ple with a high hip cir­cum­fer­ence and over­es­ti­mat­ed if the hip cir­cum­fer­ence, on the con­trary, is small com­pared to the aver­age data (this is espe­cial­ly true for women).

Waist/height index

Waist/height index

The ratio of waist cir­cum­fer­ence to a per­son­’s height, or waist / height index (WTI, WtHR) is anoth­er attempt in a sim­ple way to iden­ti­fy peo­ple with para­me­ters dan­ger­ous to health.

Accord­ing to research in this area, ITR is more effec­tive in pre­dict­ing car­diac risk, the like­li­hood of dia­betes, and all-cause mor­tal­i­ty than BMI or even ITB.

The cri­te­ria is very sim­ple:

  • if the ratio of waist cir­cum­fer­ence to height is 0.5 or less, then the per­son has a nor­mal weight;
  • if the MRI is greater than 0.5, this indi­cates the pres­ence of risks to his health.

Advan­tages of mea­sur­ing MRI: sim­ple and con­ve­nient for approx­i­mate risk assess­ments of devel­op­ing heart and vas­cu­lar dis­eases, as well as dia­betes mel­li­tus.

Cons of ITR: all the same as for oth­er indices. The fea­tures of the fig­ure and phys­i­cal activ­i­ty of a per­son are not tak­en into account.

Brock’s formula

In order to cal­cu­late the weight norm accord­ing to Brock­’s for­mu­la, it is enough to sub­tract a cer­tain fig­ure from your height. And which one depends on growth:

  • If you are 165 cm or less: Sub­tract 100 from your height.
  • With a height of 166–175 cm: sub­tract 105 from the height.
  • With a height of 176 cm or more: sub­tract 110 from the height.

But that’s not all! Con­sid­er what type of physique a per­son has. And as you know, there are three of them (main): asthen­ics (thin and tall), nor­mas­then­ics (har­mo­nious), hyper­s­then­ics (mas­sive and low). Then, when using Bro­ca’s for­mu­la, after sub­tract­ing the cor­rect fig­ure, it fol­lows:

  • Asthen­ics deduct anoth­er 10%.
  • Nor­mosten­ics — do not change any­thing.
  • Hyper­s­then­ics — add 10% on top.

But this still does not give the final val­ue. Because peo­ple come in dif­fer­ent ages, and, as men­tioned ear­li­er, their height and, to some extent, physique depend on age. There­fore, plus every­thing fol­lows:

  • For young peo­ple aged 20–30 years — fur­ther reduce the cal­cu­lat­ed fig­ure by 10%.
  • Peo­ple aged 40–45 years — do not change any­thing.
  • Elder­ly peo­ple over 50 years old — add 5–7% on top.

The idea of ​​Brock­’s for­mu­la is good: take into account age, body type, fea­tures of the fig­ure with dif­fer­ent heights — and this is a plus of this for­mu­la. It is already dif­fi­cult to call it sim­ple, giv­en the numer­ous edits that occur in the process.

There is a slight­ly sim­pli­fied mod­ern ver­sion of Brock­’s for­mu­la using a fac­tor of 1.15:

  • To cal­cu­late the weight of a woman, it is nec­es­sary: ​​sub­tract 110 from height and mul­ti­ply the result­ing num­ber by 1.15.
  • To cal­cu­late the weight of a man, you need to sub­tract 100 from height and mul­ti­ply the result­ing num­ber by 1.15.

The minus of Brock­’s for­mu­la is just in too many nuances, and also in the fact that in this case it is impos­si­ble to take into account the ratio of fat and mus­cles. The same ath­letes, preg­nant ladies and girls under 18, for exam­ple, will again be out­side the norm.


  • There is no ide­al for­mu­la for cal­cu­lat­ing the “cor­rect” weight with a min­i­mum of data and mea­sur­ing instru­ments. Peo­ple are too dif­fer­ent.
  • All these meth­ods give very approx­i­mate results, espe­cial­ly at the bor­ders of the ranges. Espe­cial­ly for peo­ple who are some­how dif­fer­ent from the aver­age per­son — height, health, body con­di­tion, etc.
  • Nev­er­the­less, these indices are quite suit­able for under­stand­ing: the risks of heart and vas­cu­lar dis­eases, dia­betes and oth­er dan­ger­ous dis­eases are already too high, and some­thing needs to be done with extra pounds.
  • A more accu­rate result can be obtained by mea­sur­ing the pro­por­tion of fat and mus­cle in the body.

Com­par­i­son of select­ed body com­po­si­tion para­me­ters in women using DXA and anthro­po­met­ric method. / Grze­gor­czyk J, Woloszyn N, Perenc L. // J Res Med Sci­ence - 2019 Aug - 28;24:70

Abdom­i­nal Obe­si­ty Indi­ca­tors: Waist Cir­cum­fer­ence or Waist-to-hip Ratio in Malaysian Adults Pop­u­la­tion. / Ahmad N, et al. // Int J Prev Med. - 2016 - 7:82

BMI-relat­ed errors in the mea­sure­ment of obe­si­ty. / Roth­man KJ. // Int J Obes (Lond). - 2008 Aug - 32 Sup­pl 3:S56‑9.

The valid­i­ty of pre­dict­ed body fat per­cent­age from body mass index and from imped­ance in sam­ples of five Euro­pean pop­u­la­tions. / Deuren­berg, P., Andreoli, A., Borg, P. et al. // Eur J Clin Nutr - 2001 - 55


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